1. Field
The present disclosure relates to the manufacture of sheet glass. More particularly, the present disclosure relates to pulling rolls for use in the manufacture of sheet glass by, for example, the overflow downdraw fusion process and methods for the manufacture thereof.
2. Technical Background
Pulling rolls are used in the manufacture of sheet glass to apply tension to the ribbon of glass from which the sheets are formed and thus control the nominal sheet thickness. For example, in the overflow downdraw fusion process (see Dockerty, U.S. Pat. Nos. 3,338,696 and 3,682,609), pulling rolls are placed downstream of the tip or root of the fusion pipe and are used to adjust the rate at which the formed ribbon of glass leaves the pipe and thus determine the nominal thickness of the finished sheet.
A successful pulling roll can meet a number of conflicting criteria. A pulling roll should be able to withstand the high temperatures associated with newly formed glass for substantial periods of time. The longer a pulling roll can last in such an environment the better, since the time required for roll replacement reduces the amount of finished glass a given machine can produce and thus increases the ultimate cost of the glass. A pulling roll should also be able to provide sufficient pulling force to control the thickness of glass sheet produced in the process and should not give off excessive amounts of particles that can adhere to the glass and form surface defects thereon.
As the performance and life expectancy of conventional pulling rolls is typically limited by the materials of manufacture, physical properties of the roll, and operating conditions, roll replacement can result in significant disruptions in the glass production process and significant costs to ship a roll to, for example, a roll manufacturer for repair or rebuilding. Conventional pulling rolls, once formed, cannot be dismantled without adversely affecting the properties and performance of the roll. Even recovery of the roll shaft for use in manufacturing a new roll can be costly and time consuming. Thus, there is a need in the art to obtain a pulling roll that can be repaired and/or rebuilt without incurring significant cost and time. This and other needs are satisfied by the methods and compositions of the present disclosure.